1. Field of the Invention
The present invention relates to an adsorption unit, an adsorption device and regeneration methods thereof, and in particularly to an adsorption unit, an adsorption device and regeneration methods thereof which incorporate electrical heating to regenerate adsorptive materials therein.
2. Description of the Related Art
Common adsorptive materials are activated carbons, activated alumina, silica gels, and zeolites. Adsorptive materials are able to adsorb volatile organic compounds (VOCs) or moisture from the air. Adsorptive materials are formed with structures comprising macro-pores (with pore size greater than about 50 nm), meso-pores or micro-pores (with pore size smaller than about 2 nm), and are able to function as adsorbent with a high specific surface area, such that molecules of the VOCs or moisture can be adsorbed on a surface of adsorption materials by Van der Waals forces. Adsorption materials are typically used in an adsorption device having a multi-tower configuration or a rotary wheel configuration for performing a continuous operation.
When the adsorptive materials in the adsorption device achieves saturation, thermal convection is typically used to break the Van der Waals bonding between the adsorptive materials and the adsorbates, thereby desorbing molecules of the adsorbed VOCs or moisture from the surface of the adsorptive materials to completing the regeneration. Adsorption and desorption processes may be repeatedly applied to the adsorptive materials to provide removal of peculiar smells and dehumidification of air.
However, by thermal convection, the air needs to first be heated in regeneration method, and desorption is achieved by heat transfer between the heated air and the adsorptive materials. Due to heat loss being easily caused, in the processes for heating the air by a heater and transferring the heated air to the adsorptive materials for desorbing thereof, and heating the air with unsatisfactory heating efficiency of the heater, desorption process require great amounts of power consumption. In addition, in a size-reduced adsorption device, there is always not enough space for installing a heater with enough area for heat-exchange. As a result, additional radiation heat loss is usually caused due to an extreme high temperature of the heater surface during heating of the air.
FIG. 1 illustrates an energy consumption analysis of a conventional condensing dehumidifier for a household using a desiccant wheel as disclosed in Taiwan Patent Application Publication No. 201026374. Due to an extreme high temperature of a heater surface used therein, most of the energy consumed by the heater is dissipated in the form of radiation. In the power consumption analysis of a conventional condensing dehumidifier for a household, a condensing amount is about 6.6 liters/day (20° C., 60% RH), and a power consumption of the heater is about 600 watts, wherein 479 watts therein are for radiation heat, and only 121 watts are used for heating the air.
FIG. 2 is a method of low energy consumption for desorption as disclosed in Taiwan Patent Application Publication No. 201026374. The method couples electrode structures 31 and 32, for example reticular metal electrodes 31, on both sides of a dehumidifying material 30, and a voltage source 33 can be applied thereto by contact thereof with a brush 330, thereby causing electron excitations of the water molecules in a regeneration area, such that the water molecules obtain energy for desorbing from the adsorbents. However, the regeneration ability of method depends on the electrical conductivity between the adsorbates such as VOCs or moisture and the adsorptive materials. Since the adsorptive materials are irregular porous structures, and the generated energy may cause various regeneration issues due to various electrical conductions and heating issues during application of the electrical energy to the adsorptive materials bonded with water molecules, regeneration and desorption effects of the adsorption device are reduced. In addition, the reticular metal electrode 310 in the electrode structures 31 and 32 may block a channel for regeneration, thereby reducing effective surface area for regeneration desorption process.